What Is It?
The most prominent symptom of major depression is a severe and persistent low mood, profound sadness, or a sense of despair. The mood change can sometimes appear as irritability. Or the person suffering major depression may not be able to take pleasure in activities that usually are enjoyable.
Major depression is more than just a passing blue mood, a "bad day" or temporary sadness. The mood changes that occur in major depression are defined as lasting at least two weeks but usually they go on much longer — months or even years.
A variety of symptoms usually accompany the mood change, and the symptoms can vary significantly among different people.